Right now, I'm using Grammarly. They at least fix the spelling and the latest update, although not so useful for posts, can really help with comments. It analyzes the tone.

For people who use Word Press, Yoast is really great. I'm still looking into sites where you can copy-paste or analyze Steem blogs. It would be really great if Steemit or Steempeak integrated one of the popular tools for this. The Google SEO ranks will really shoot up quickly if people are using it.